Truck control with memory relay



April 20, 1954 H. A. MUDD TRUCK CONTROL WITH MEMORY RELAY Filed Oct. 28.1949 HTTOPNE/S.

/A/l ENTO/? HHRRY 4. Muoa,

QEN QQM I FC Patented Apr. 20, 1954 TRUCK CONTROL WITH MEMORY RELAYHarry A. Mudd, Maplewood, Mo.,

assignor to McQuay-Norris Manufacturing Company, St. Louis, Mo., acorporation of Delaware Application October 28, 1949, Serial No. 124,103

11 Claims. 1

The present invention relates to a control such as those used forcontrolling the speeds of trucks thatare driven by electric motors.Specifically, the present invention is animprovement over the truckcontrol shown in the application of Lawrence M. Persons, Serial No.41,695, filed July 30, 1948, for Multi-Speed Truck Control, and assigned.to the assignee of the present application.

In a multi-speed truck control providing several rates of speed for bothforwardv and reverse direction of travel, the problem exists that, whenthe control is suddenly shifted from a high speed operation in onedirection to the position in which it is to obtain high speed operationin the other direction, there may be a sudden overload on the drivingmotor, attempting to make the motor reverse itself against the momentumof the truck. It has heretofore been proposed to control this by theeiiects of dynamic braking. For instance, in some controls suddenreversal of the control lever energizes a dynamic braking circuit thatwill hold until the motor substantially stops, which dynamic brakingcircuit includes hold-out relays that prevent energization of thecircuits to drive the motor in the opposite direction until the truckhas stopped its initial movement, and then only after the controller isonce again neutralized and reset for drive in the new direction. Thedifliculty with such controls is that they fail to accommodate acondition where the operator, driving the truck in one direction, firstreverses the controller, but then changes his mind and returns thecontroller to a driving position in the initial direction. Presentcontrols, such as suggested have the characteristic that once thecontroller has been reversed from its initial direction they block outfor any drive in either direction until the truck is actuallysubstantially stopped. Therefore, it is impossible to return,

the drive to the initial direction without sub,- stantially stopping thetruck, even though a return in the initial direction does. not overloadthe truck motor.

It is an object of the present invention to overcome this deficiency informer controls by having means that prevent a reversing energization ofthe motor until it has substantially stopped movement in its initialdirection, but which does not interfere with instant reenergization ofthe motor for further drive in its intial direction. In one sense of theinvention, it is an object to provide a delaying means that will delay areversing energization of the drive motor until it has slowed downsufiici'ently to avoid overload, but which will not delay any repeatenergization of the motor in its initial direction.

It is a further object to combine the foregoing functions with dynamicbraking so as to prevent the control mechanism from responding to areversing shift of the operating member until the dynamic braking hascaused the truck substantially to stop; but which does not interferewith the immediate reenergization of the motor in response to a returnof the operating control member to a high speed position in its initialdirection.

Another aspect of the objects of the invention is to provide a controlfor a motor driven, reversible truck that will provide dynamic brakingwhenever the operating control is moved from a driving position ineither direction down to neutral, and which, when the operating controlis moved from a driving position in one direction to a reversing drivingposition, will provide dynamic braking and will prevent reversingenergization of the motor until the truck has substantially stopped, butwhich will eliminate dynamic braking and will provide immediatereenergization of the motor if the operating control, after suchneutralization, is again returned to a driving position in its originaldirection.

In particular, this control has a controlling relay that must be closedto enable the truck motor to become energized at all when the controlleris moved from neutral position to a driving position for operating themotor in either direction, and it has means interconnected with thedynamic braking circuit that prevents closure of this relay when thecontroller is moved from a driving position in one direction to areversing driving position, but which does not so act when thecontroller is moved to neutral and back to a driving position in itsinitial direction.

As this control is basically similar to the previously mentioned Personscontrol, I have here illustrated it following in practically all casesthe reference numbers shown in that previous application, adding theretothe ones necessary to illustrate the improvements herein disclosed.

The drawing is a diagrammatic showing of the control.

Referring to the diagrammatic view, there is a truck drive -motor 350that is shown as series wound, it having a field winding 35! and adivided resistance 352 and 353 in series with the rotor. This motor 359is a reversible direct current motor that is operated from a battery355. It is reversed by reversing the direction of current through itsfield winding and its speed is regu- 3 lated by varying the amount ofresistance put in series with its armature. This latter involves theselected use of both, either, or neither of the two resistances 352 and353.

There are two primary solenoid control switches 360 and 36i that act ascrisscross interlocking switches to determine the direction of currentflow through the field winding 35i and hence the direction of rotationof the drive motor 350. The solenoid switch 360 is energized to produceforward rotation of the motor 350, whereas the solenoid switch 36! isenergized to produce reverse rotation.

There are two additional solenoid switches 362 and 353 that control thespeeds of the driving motor and, as it will appear, provide four speedsin each of the chosen directions.

The winding connections for the motor in-.

clude a positive battery line 460 and a negative battery line 40!. Thepositive battery line is connected by a lead 403 to one side of themotor armature. The other side of the armature of the motor 350 isconnected directly into one end of the resistance 352 and is alsoconnected by a line 404 to one of the contacts 383 of the speed controlsolenoid switch 363.

The other end of the resistance 352 is connected by a line 405 thatleads to one of the contacts 318 of the other speed control solenoidswitch 362. As is evident, the contacts 383 of the solenoid 363 areclosed when the coil 380 of that solenoid is energized. Similarly, thetwo contacts 318 of the speed control solenoid switch 362 are closedwhen the coil 315 thereof is energized. In the released position of thesolenoid switch 363, its two contacts 382 are closed by its armature381. In the released position of the solenoid 362, its two contacts 311are closed by its armature 316.

The upper end of the resistance 353 connected into the rotor of thedrive motor 350 is connected to a wire 406. This wire 406 connects tothe outside ones of the released contacts 311 and 382 of the two speedcontrol solenoid switches 362 and 363. The two inside ones of thecontacts 311 and 382, as well as the two inside ones of the energizedcontacts 313 and 383, are all connected together by a connection 0.

As illustrated, the directional control solenoid switches 360 and 36!have both released and energized switch contacts. The solenoid 360 has acoil 365 that, when deenergized, releases an armature 366 to close thecontacts 361. When the coil 365 of the solenoid 360 is energized, itsarmature 366 closes together the two contacts 368.

In similar fashion, the directional control solenoid 36I has an armature31! controlled by a coil 310. When the coil 310 is deenergized, thearmature 31! closes together two contacts 312. When the coil 310 isenergized, it closes together two contacts 313.

It will be observed that the two adjacent contacts 361 and 312 are bothconnected to the previously mentioned line 406. The two adjacent ones ofthe contacts 368 and 313 of the solenoids 360 and 36! are connectedtogether and are joined to a wire 40! which is the negative lead of thebattery 355.

The upper end of the field coil 35! is connected by a wire 408 thatleads to both of the two upper outer ones of the contacts 312 and 313 ofthe solenoid 36L The lower end of the field winding 35! is connected toa wire 409 that leads to both of the two outer ones of the contacts 361and 368 of the solenoid switch 360.

The coil 365 of the solenoid switch 360, when energized, closes a switch360. Similarly, when the coil 310 of the solenoid switch 368 isenergized, it closes a switch 314.

The direction of movement and the speed of movement of the drive motor350, as already stated, are controlled by the four solenoid switches.These solenoid switches are, in turn, controlled by a control mechanismthat has a main control handle that is manually operated. The major partof this section of the present control is shown at the right of theschematic drawing.

The control 10 is preferably one that is manually operated in the mannershown in the Persons application previously referred to. Fordiagrammatic purposes, it is shown as being mounted for rocking movementon a shaft and as having a double cal-r1440. When the arm 10 is rockedin either direction from its neutral position illustrated, one or theother sides of the cam 440 will cause a cam follower device 44! to bemoved. In the actuation of the control, the cam follower mechanism 441is moved down to actuate a group of sequence switches that obtainmovement of the truck motor 350 and increase its speed. When thecontroller 10 is returned,

the follower mechanism 44! moves upwardly, reduces the speed of themotor 350, and finally can neutralize it or stop it.

The cam follower mechanism 44! has four cams. on it illustrated at 210,H3, 2, and 214, reading from right to left in the drawing. These camdevices 240, H3, 21! and N4 actuate four switches 200, 20I, 203 and 204,respectively. It will be seen that the cam 210 closes the switch 200upon movement of the arm 10 in either direction from neutral, andmaintains the switch 200 closed whenever the arm 10 is out of itsneutral position. The cam 2 l3 closes the switch 20! only when the arm10 is in its first speed position. The cam 21! closes the switch 203when the arm 10 is moved to its second speed position,

holds the switch 203 closed when the cam is continued into its thirdspeed position, but then reopens it when the arm 10 is moved to itsfourth speed position. The cam member 2l4 closes the switch 204 onlywhen the arm 10 is moved to its third speed position and maintains theswitch 204 closed as the arm 10 is moved into its fourth speed position.

The controller 10 also actuates a forward and reverse switch arrangementthat is illustrated to the left of the controller 10 in the diagrammaticview. There is a pair of mechanically coupled forward switches 205 and500 that are closed only when the controller 10 is moved as farcounterclockwise as the position marked Fo11ward .-in.

the drawing. There is also a pair of mechanically coupled reverseswitches 202 and 50! that are closed only when the controller 10 ismoved as far as the position marked Reverse in the drawing. It will benoticed that these switches are actuated before the controller 10 closesany speedregulating switches. When the arm 10 is in its neutralposition, all of the four switches are open.

The control also includes a blocker relay 294 having an actuatingrocking lever or armature 306 that is pivoted at 304. Adjacent one endor the armature 306 are two contacts 309 and 310,

and adjacent its other end are two contacts 3| I This armature 306 isnormally spring urged to the position shown, closing the contacts 309and 380 together, by a spring 3| re and 3l2.

5 lay 294- has two coils 295- and 296. The coil 295 will draw thearmature 306- into position such that its armature 306' closes thecontacts 3 and 3|2. The coil 296 is a bucking coil that pposes theoperation of the coil 295, or, as illustrated in the diagram, it is acoil that holds the armature 306 in position wherein it closes thecontacts 399 and 3H! and holds the. contacts 3 and 3|2 open. When thecoil 299 is fully energized, the coil 295, even when it also isenergized, cannot shift the armature 306.

There is also what is called a memory relay illustrated at 502' in thediagram. This relay includes. an armature that is rockable to closeeither of two switches 505 or 506- and to open the other. There are twocoils 503 and 504. The coil 503 will draw the armature in position toclose the switch 505, whereas the coil 504 will draw the armature toclose the switch 503. The coils 503 and504 are mounted about permanentmagnet cores, there being such a core 501 associated with the coil 503,and, a core 508 associated with the coil 504'. Each core is ofinadequate strength to tip the armature from either position to theother, but each will hold the armature in either operated position afterit has been displaced into such position by suitable energization of thecorresponding one of the two coils 503 and 504.

The secondary parts of the control are interconnected with the primarycontrol. The negative side of the battery has a line 492 that leads toeach of the four switches 209, 20|, 203 and 204. The switch 209 is alsoconnected by a line 429 that leads in one branch through. the blockingrelay coil 295, the other side of which is connected to a line 42| thatleads to the line 400 on the positive side of the battery. The line 420from the switch 290 in another branch is connected by a line 422 that,in turn, is connected to one side of each of the two solenoid operatedholding switches 369 and 314. The other side of both of these switchesis connected by a line 423 that leads back to the secondary part of thecontrol, and thence one branch of the line 423 is connected into oneside of each of the forward and reverse switches 205 and 202. Anotherbranch from the line 423 is shown at 424 and leads to the contact 3|2 ofthe blocker relay 294. The switch 29| of the speed regulating group isconnected by a line 430 to the other terminal 3l| of this blocker relayswitch.

The other cam operated switch 293 is connected by a line 432 that leadsinto the coil 315 of the solenoid 352. connected to the line 400 on thepositive side of the battery.

The switch 204 is connected by a line 43-3 that leads to one side of thecoil 380 or the solenoid 363, the other side of which is. alsoconnected-to the line 509 on the positive side of th battery.

The other side of the forward switch 2051s connected by a line 425 that.leads to one side of the coil 365 of the solenoid 369, the other side ofwhich is connected to the line 409. The other side of the reverse switch202 is connected by a line 425' that leads to one side of the coil 370of the solenoid 36L the other side of which coil is connected to theline 000.

The upper end of the resistor 353- in series with the armature windingof th motor 350 is connected by a line 5H1 that, in turn, is connectedto one side of each. of the forward and reverse switches 500 and EM. Theother side of the switch 500 is connected by a line 5| I that leads Theother side of this coil is r 6. to one end of the coil 5030f the memoryrelay, and also includes a branch 5|6 that leads to the switch 506 ofthe memory relay. In similar fashion, th reverse switch 50l is connectedby a line 5|4 that is connected to one side of the memory relay coil 504and is also connected to one side of the switch 505 of the memory relay.The other sides of the two coils 503 and 504 are connected by a line 435that leads back to the lower side of the resistance 352. The other sidesof the two switches 505 and 506 are connected by a wire 5|? that leadsto the terminal 309 of the blocker relay. The other side 3|0 of thisswitch of the blocker relay is connected by a wire 5|8 into one end orthe coil 290. The other side of this coil is connected to the wire 42|that leads back to the wire 400 on the positive side of the battery.

Operation When the control is completely at rest, its components occupythe positions indicated in the drawing. The motor 350 is entirelyinactive and its field winding short-circuited upon itself. The varioustruck controlling solenoids 360-363 are in their released positions. Theholding switches 309 and 314 are open. The main control handle 70 is inits neutral position so that the switches 200, 20L, 203 and 204 areentirely open and the switches 202 and 205, which are the directionalcontrol switches, are also open, as are their related switches 500 and50!. The blocking relay armature 306 is operated by the spring 3|! tothe position shown with the contacts 3| |3| 2 open and the contacts309-3|0 closed. The memory relay 502 may be in the position shown, butits actual position will depend upon the direction of travel of thetruck when it was previously operated before the stop. It is retained inits position by the action of the near end of its armature to one of themagnetic cores 501'and 503.

If the operator desires to move the truck forward, he first moves thehandle 10 counterclockwise, as, for example, to the first speedposition. In this operation, the handle first passes the position markedForward and in so doing it closes the switches 205 and 500 while leavingthe switches 202 and 50| open. The movement of the arm 10 to the firstspeed position, by the action of the cam 440 upon the arm 441, causesthe switches 200 and 20! to be closed subsequently to closure of thedirectional switch 205 and the memory relay control switch 500.

When the switches aforesaid are closed, circuits are established fromthe battery 355. The negative lines 40| and 402 are constantly connectedto the negative side of the battery. The line 402 leads to the secondaryside of the control and to the several switches 200, 20|, 203 and 204.With the switch 209 closed, the circuit from the negative line 462passes through that switch, thence through the line 420, the coil 295,the line 42| and the positive line 400 of the battery to the positiveside of the battery. This action energizes the coil 295 and draws thearmature 395 of the holding switch against the spring 3|! to close thecontacts 3H and CH2 and to open the contacts 309 and 3|0.

When the blocking relay closes the contacts 3| and 3| 2, a circuit fromthe negative line 402 then flows through the now closed switch 20|, theline 430, the contacts 3|! and 3|2, the line 424, the line 423, thedirectional switch 205, the line 425, the coil 365 ofthe forwardsolenoid switch300,

7 and the line 400 back to the positive side of the battery.

When the coil 365 is energized, it draws its armature 366 to open thecontacts 361 and to close the contacts 308 of this directional solenoidrelay 360. Also it closes the switch 369. When the switch 369 is closeda circuit shunting the switch 201 is established, this circuit beingdependent only on continued energization of the coil 355 of the relay360 and closure of the switches 200 and 205. It renders the continuedenergization of the relay 360 independent of the switch 201 andindependent of the position of the armature 305 of the blocking relay.Stated differently, and, as will appear, it requires operation of thecontrol through first speed position when the direction of travel isreversed.

When the directional relay 360 is so operated, the drive motor 350 iscaused to move in a forward direction at a first low speed. Its primarycircuit is as follows, beginning with the negative side of the battery:The line 401, the contacts 366 through the contact 306, the line 409,field winding 351, the line 405, the contacts 312 through the contact311, the line 406, the resistances 353 and, 352 in series, the rotor ofthe motor 350, the line 403 and the line 400 to the positive side of thebattery. In this, the direction of flow of current through the fieldwinding 351 is upwardly in the drawing. The entire resistance 353-352being in series, the motor 350 operates at only a a low speed.

The resistance drop across the resistor combination 353-352 is alsoapplied across one of the coils of the memory relay 502. Starting at theupper end of the resistor 353, there is a circuit beginning with theline 510 that extends to the switch 500 that is part of the directionalswitch combination operated by the controller handle 10. From the switch500, the circuit continues through the line 511 and the coil 503 of thememory relay. This is a high resistance coil. The circuit continuesthrough the line 435 that extends back to the bottom of the resistor352. The foregoing resistance drop is suiicient to cause the coil 503 topull the armature over to close contacts 505 and open the contacts 506.As soon as the armature has thus shifted, the coil 503 may bedeencrgized and the permanent magnet core 501 within the coil 503 willhold the armature in the position described. No circuit combinations ofthe switches 505 and 506 are affected at this time. If the handle 10 ismoved to its second speed position, the switch 200 will remain closed.The switch 20! is opened, but this has no effect because of thepreviously mentioned holding circuit through the switch 369 of thedirectional solenoid 360. The switch 203 will be closed by the cam 2Hwhen the second speed position is obtained.

Closure of the switch 203 establishes a circuit from the negative line402 through the switch 203, the line 432 to the coil 315 of the solenoidswitch 332, and thence to the positive line 400 leading to the battery.Energization of the coil 362 shifts its armature to open the contacts311 and to close the contacts 318. This will be found to shunt out theresistance 353. The motor circuit is then from the line 401, thecontacts 368, the line 403, the field winding 351, the line 408, thecontacts 312, the line 406, the contacts 302, the line 410, the contacts318, the line 405 to the top of the resistance 352, thence through thatresistance and the motor 350 to the line 400 8 in the positive side ofthe battery. The shunting of the resistance 353 causes the speed of themotor 350 to increase so that the truck or other vehicle can movefaster.

If the operator moves the handle 10 to the third speed position, theswitches 200 and 203 remain closed and the switch 204 is also closed.Closure of the switch 204 completes the circuit from the negative sideof the battery through the line 402 through the switch 204, the line433, the coil 380 of the solenoid switch 363, and the line 400 to theother side of the battery. When the coil 330 is energized concurrentlywith the energization of the coil 315 of the solenoid switch 362, theresistance 352 is shunted out and the resistance 353 alone is left inthe motor circuit. The motor circuit then is as follows: From thenegative side of the battery, the line 401, the contacts 368, the line409, field winding 351, the line 408, the contacts 312, the line 400 tothe upper end of the resistance 353, the line 405 from the lower end ofthe resistance 353, the contacts 318, the line 410, the contacts 383,the line 404 through the rotor of the motor 350 and the lines 403 and400 to the other side of the battery. As illustrated, the resistance 353is less than the resistance 352 so that the speed of the motorincreases.

If the operator moves the handle 10 to the fourth speed forwardposition, this action will maintain the switches 2130 and 204 closed butwill open the switch 203. As the switch 203 directly controls the coil315 of the solenoid switch 362, its being open will deenergize the coil315 and permit the armature 316 to shift from the contacts 318 back tothe contacts 311. Otherwise, the various switches remain as before.However, this change completely shunts out both resistances 352 and 353from the motor circuit which becomes as follows: from the negative sideof the battery through the line 401 to the contacts 368, the line 409,field winding 351, the line 406, the contacts 312, the line 406, thecontacts 311, the line 410, the contacts 383, the line 404, the armatureof the motor 350, and the lines 403 and 400 to the positive side of thebattery. The drive motor 350, therefore, operates at maximum speed.

If the handle 10 of the control is moved downward to a lower position,it will cause the truck to reduce speed. If the handle is returned allthe way to the neutral position, the motor 350 will be disconnected fromthe battery. However, dynamic braking will be efiective to cause thetruck to slow down and ultimately to stop. As aforesaid, the fieldwinding 351 is short-circuited upon itself by the release of all of thesolenoid switches 360-363, and, when the handle 10 is returned toneutral, the solenoid switches are thus released to the positionsillustrated. The circuit through the field winding 351 can be tracedfrom it through the line 408, the contacts 312, the line 406, thecontacts 361, and the line 409 back to the other end or the fieldwinding.

With the truck geared to the motor 350, the motor will be driven andwill act as a generator.

. A circuit for dynamic braking can be established as soon as theblocking relay 294 is released. That is to say, as soon as the coil 265becomes deenergized by neutralization of the handle 10, the spring 311will swing the blocking relay over to the position wherein it closes thecontacts 309 and 310. Thereupon, a dynamic braking circuit isestablished from the top of the motor 350 through the line 435, the coil504, the line 514, the previously closed contacts 505, the line 511, thecontacts 309 and 310, the line 518, the block- .9 ing coil 296, the lineM l, and the lines 480 and 4-03 back to the motor. The current thussupplied to the coil 584 during dynamic braking is insufficient toovercome the permanent magnet in the coil 503 so that the memory relayis not shifted by the dynamic braking operation.

In order to operate the truck in a reverse direction, .the handle it ismoved clockwise in the drawing, as, for example, to the first speedreverse position. In so doing, it passes through the position indicatedRe-verse and at such time closes the switch combination 2 6258 i Thecain action on the cam follower arm M! and the switches 20;), 2E1, 263and 2:24 is identical for the several speeds in reverse that it is forthe corresponding speeds in the forward direction. Ihe switch 2 02,however, closed in. place of the switch 2&5, energizes'the solenoidswitch (it! instea-dof the solenoid so :thatin the reverse position thecircuit combinations for the several speeds are identical as intheforward direction, except that the flow or cur-rent through the fieldwinding 35'! is in the opposite direction. Also, the switch lit!energizes the memory relay in the opposite direction.

To illustrate, for the first speed in reverse, the movement of the leverl5! closes the switches 2'82 and 50! and also closes the switches 2G5}audit-I. Closure of the switch i ll'li'esta blishes the circuit from thenegative line 402 through the switch 280, the 'line 42 0, the coil 295,and the lines 42'! and 488 to thebattery to energize the coil 295 andoperate the blocking relay as previously, Similarly, the closure oftheswitch 2'3! initially establishes a "circuit from the negative line402 through the switch 2 81, the line 430, the contacts 3! l and 3|2,the line'42'4,'the line 423, the reverse switch. 262, the line 426, thecoil are of the solenoid switch till and "the line ills back to thepositive side of the battery. This energizes the solenoid 365i, drawsits armature 37% to close the contacts EH3 and open the contacts 312,and it also closes the holding switch 314. When the switch 31 is'closed,the foregoing circuit to the coil 370 is held as before through theswitch 266 to the line 422, the switch 37 4, the line 423, the switch292, the line 426 to the coil 31B and the return battery line s99, thusshunting the blocking relay.

The primary circuit to the drive motor 350 now extends from the negativeside of the battery through "the line 401, the contacts 313, the lineMB, downward through the field coil 35L thence through the line wfi, thecontacts 361,

the line "406 through the two resistors 3'53 and 352, the motor 350 andthe lines 403 and 406 back to the positive side of the battery.

As before, the resistance drop across the two resistors 35? and 353 isthen placed onto the memory relay. This circuit is from the top of theresistor 353 through the line 5H), the switch 50!, the line 514, thememory relay energizing coil 504, the line 435 to the bottom of theresister 35.2. This will energize the coil 504 and cause it to pull thearmatureof the memory relay over to the position shown wherein it closesthe contacts .506 and opens the contacts 595. The permanent magnet inthe memory relay will be sufficient :to hold the armature in theposition indicated until the coil :503 is subsequently similarlyenergized.

- It is not necessary to trace the several reverse speed positionsbecause they are the :counterparts 0: theforward speed positions, saveonly 10 that the solenoid 361 is energized in .place of the solenoid360.

If from one or the reverse speed positions, the operator returns thehandle abruptly to neutral, dynamic braking will result. All of thetruck solenoid switches will be released, and the several cam operatedswitches on the control handle mechanism will be opened. The blockingrelay will return to the position shown. The memory relay 502 will holdthe position shown because the deenergization of the coil 5M merelyleaves the memory relay under the control of the permanent magnet 5B8associated "with the coil 504. When the truck overrides the motor 350with the control lever '10 in its neutral position, the dynamic brakingcircuit will be the counterpart of that obtained in the forward travel.It starts from the top of the motor 350, extends through the line 435 tothe coil 593, thence by way of the lines 5. and 5:6 through the closedswitch 506, the line 511 through the released blocking relay, and thencebyway of the line 5l8, the coil .1296, the line I and the line 460 tothe bottom of the motor.

The dynamic braking circuit includes the coil 503, which is a highresistance coil, in series with the relatively low resistance pluggingcoil 2%. The high resistance of the .coil "5113 provents the pluggingacoil 29B 'from holding the blocking relay against an energization ofthe coil 295. If the handle 10 is moved from the reverseyside to theiorwa'rd side, the first action in displacement in the forward directionis a closure of the switches 205 and #5130. As soon as the switch 500 isclosed, a di-lferent dynamic braking circuit is energized, whichsubstitutes the low resistances 352 and $53 in series with the pluggingcoil 296 in place of the coil 503. This circuit is as follows: From themotor 1350 through the resistors 3-52 and 353, the line 519, the switch'51"], the line 511, the line 5l6, the switch 506, the line 517, thecontacts 309, 310, the line 5l8, the coil 2%, the line 421 and the lines400 and 403 back'to the motor. The low resistance of this circuitproduces sufiici'ent energ-ization of the coil 2% to hold the armatureof the blocking relay in the position shown, and to prevent the closureof the contacts 3H and (H2, regardless of subsequent energization of thecoil 295, until the motor slows down. Thus, when the truck 'has beenrunning in the reverse direction, and the handle is suddenly thrown overto the forward direction, there is an mediate blocking of the control sothat the motor 358 cannot be energized in the forward direction until ithas slowed down and substantially stopped. This also produces dynamicbraking.

If the handle l0 from a reverse position is neutralized and thenreturned to the reverse direction, the plugging relay coil 296 will notbe energized through the last named circuit. The dynamic braking circuit"will continue as originally by way of the line 4-35, the coil 593, thelines *5 and 51-6, the switch "506 the line 5H, the switch 3 H), theline '5 T8, the coil 2E6, the lines 42!, 400 and 403, back to the motor.However, a reclosure-or the reverse switch '50! will not energize theparallel dynamic braking circuit that energizes the plugging coil 296sufficiently to hold the blocker relay in its open position illustrated.The former circuit which began with the resistors #52, 3'53, andwhenthrough the line 510 new passes through the closed switch '50! andthe line 51! backto -the :memory relay.

()wing to the initial energization of the memory relay to the positionshown when the arm l was first moved to the reverse direction, theswitch 505 will remain open, thus breaking the alternative or parallelcircuit that adequately energizes the plugging relay coil 296 to preventa pull-in by subsequent energization of the coil 295. Hence, the returnor repeat movement of the arm 19 in the reverse direction to one of itsfour speed positions will at once reenergize the coil 295 and that coilwill have power enough to pull the blocking relay to the positionclosing the contacts 3 and (H2. The memory relay acts in directcounterpart when the control has been in a high speed reverse positionand is shifted to a forward position.

Thus it may be seen that the memory relay will actually block out anyattempt to reverse the potential applied to the motor 350 when theoperating handle 19 is moved from a high speed position in one directionto a position in the other direction until the motor has slowed downsufficiently to stop generating enough current to energize the blockingrelay coil 296 sufiiciently to hold the blocking relay open; but thememory relay, having previously been positioned, will not act to preventa shift of the blocking relay when the handle is moved to neutral and isthere-, after returned to a speed position. in the same direction aspreviously occupied.

It may be noted that, if the operating handle is moved from a high speedposition in one direction across neutral to a speed position in theother direction, dynamic braking will be obtained, and also the controlwill be blocked out to prevent revers energization of the motor; butthat, if the handle is then returned to a speed position in its initialdirection before the truck has stopped moving, the blocking isineffective and energization of the motor for such initial direction oftravel will obtain. Also, dynamic braking follows when the handle isonly neutralized, but blocking does not occur.

Another feature of the truck control is that, when the direction of thecontrol handle 19 is suddenly reversed from one direction to a highspeed position in the other direction, the motor cannot be energized forsuch high speed operation in the opposite direction even after dynamicbraking has caused the motor to stop. The operator must take the controlthrough a first speed operation in the other direction before he canobtain higher speed operations in such direction.

The foregoing comes about because the control requires an initialclosure of the switch 29! whenever the handle 19 is moved from neutralposition, as a prerequisite to the energization of either the solenoidswitch 360 or the solenoid switch 96!. If, during operationof the motorin one direction, the handle is crossed over to a second, third, orfourth speed position in the opposite direction, the blocking operationof the coil 296 will be effective to prevent closure of the blockingrelay contacts 3 and 3l2 until the motor has substantially stopped.Hence the starting; circuit for energization of either solenoid coil 365or 319 is not closed, even when the manual switch 201 is momentarilyclosed during displacement of the handle 10 to a second or higher speedposition. The switch 2!, though momentarily closed, is reopened as thehandle is moved on to a second, third or fourth speed position.Subsequent release of the blocker coil 296 when the dynamic braking andblocking effect is over does not proceed to a shifting of the relay tit)294 because the coil 295 is not in circuit when the switch 29! isopened. The operator must then return the control handle 10 to the firstspeed position before he can obtain any operation in the oppositedirection. This avoids an overload of the motor. It will be noted thatthis effect is not true when the handle 19 is returned to operation inits initial direction. The neutralizing of the handle does not producethe blocking effect, so that a return in the initial direction willenable the coil 295 to be energized whenever the switch 291 is closedand an upper speed position will result in an upper speed energizationof the motor 350.

It may be noted that the foregoing effect may also be combined with thearrangement in the Persons application, in which the blocking relaymechanically prevents movement of the switches above first speedposition in a reversing direction.

The truck can still be plugged back and forth between first speedforward and first speed reverse without being blocked because the amountof current passed through the blocking coil 296 when the truck is movingonly as fast as the first speed positions provide is not enough to blockout the action of the coil 295 in closing the blocker relay 294 toestablish energization of one of the two solenoids 360 and 31 l. Theplugging operation is required because in maneuvering a truck in narrowspaces it is frequently necessary to move quickly in opposite directionsfor very short distances.

It will be seen that this truck control provides the mechanism wherebythe objectives set forth in the preceding specification are obtained.

In the claims to follow, the terms forward and reverse are employedmerely to distinguish the two opposit directions of movement of themotor, and without being intended to mean movement frontward andbackward with respect to the normal front of the object operated by themotor, or the clockwise or counterclockwise direction of rotation of themotor shaft.

What is claimed is:

1. In a control for a reversible electric motor, control means movableto forward, neutral, and reverse positions, circuits operated by thecontrol means in its forward and reverse positions to produce forwardand reverse energization of the motor, the control means opening saidcircuits when in neutral position; means to prevent the reverse circuitfrom being operated when the control means is moved to reverse positionduring operation of the motor in forward direction, means todisestablish the preventing means when the control means is returned toforward position during continued forward operation of the motor,whereby the control means may reclose the forward circuit, forward andreverse dynamic braking circuits energized by operation of the motor asa generator; said dynamic brake circuit including switch means movableto close either forward or reverse dynamic brake circuit contacts,preset means operable upon energization of the forward motor circuit tooperate said switch means into closing position in the reverse dynamicbrake circuit, and into opening position with respect to the forwarddynamic brake circuit and operated by energization of the reverse motorcircuit to operate said switch means into closing position in theforward dynamic braking circuit and into opening position with respectto the reverse dynamic braking circuit; means operable by displacementof the control means.

amogcos .13 from one directional position to the other to close theopposite dynamic brake circuit through the preset means; and meansinsaid dynamic braking circuits to prevent energization of the motorcircuits during energization of the dynamic brake circuit, andadditional dynamic brake circuit means closed when the control means ismoved to neutral position.

2. In a control for a reversible electric motor, control means operableto forward, reverse, and neutral positions, a forward motor energizingcircuit operated by operation of the'control means to forward position,a reverse motor energizing circuit operated by operation of the controlmeans to reverse position, the control means being-adapted to open saidcircuits when it is in neutral position; a dynamic braking circuitincluding means to prevent closure of the forward or reverse motorcircuits when the motor is oper ating as a generator, said dynamic brakecircuit including two branches for comiection with the motor to beenergized by the motor running as agenerator, comprising a reversebranch adapted to be established through the control means in reverseposition and a forward branch adapted to be established through thecontrol means in forward position, and preset means to close the reverse-dynamic brake circuit branch and open the forward dynamic brakingcircuit branch when the "forward motor circuit is energized, and meansto-close the forward-dynamic brake circuit branch and open the reversedynamic brake circu-it branch when the reverse motor circuit is closed,whereby the means to prevent closure of the motor circuits is effectivewhen the control means is displaced during operation of the motor in onedirection, to a position to produce operation of the motor in the otherdirection, but is inefiective to prevent reenergization of'a motorcircuit to operate the motor in its initial direction.

3. In a control for a reversible electric motor, control means operableto forward, reverse, and neutral positions, a forward motor energizingcircuit operated by operation of the control means to forward position,a reverse motor energizing circuit operated by operation of the controlmeans to reverse position, the control means being adapted to open saidcircuits when it is in neutral position; a dynamic braking circuitincluding means to prevent closure of the forward or reverse motorcircuits when the motor is operating as a generator, said dynamic brakecircuit including two branches comprising a reverse branch adapted to beestablished through the control means in reverse position and a forwardbranch adapted to be established through the control means in forwardposition, and preset means to close the reverse dynamic brake circuitbranch and open the forward dynamic braking "circuit branch when theforward motor circuit is energized, means to close the forward dynamicbrake circuit branch and open the reverse dynamic brake circuit branchwhen the reverse motor circuit is closed, whereby the means to preventclosure "of the motor circuits is effective when the control means isdisplaced during operation of the motor in one direction, to a positionto produce operation of the motor in theother direction, but isineffective to prevent reenergization of a motor circuit to operate themotor in its initial direction, and additional dynamic braking circuitmeans operable when the control means is moved'to neutral position andthe motor is operated as a "generator.

4. In a :controliior a reversible electric motor, control means operableto forward, reverse, and neutral positions, a forward motor energizingcircuit operated by operation of the control means to forwardposit-ion,a reverse motor energizing circuit operated by operation of the controlmeans to reverse position, the con-trol means being adapted to opensaidcircuits when it is in neutral position; a dynamic braking circuit including means to prevent closure of the forward or reversemotor-circuits when the motor is operating as a generator, said dynamicbrake circuit including two branches comprising a reverse branch adaptedto be established through the control means in reverse position and aforward branch adapted to be established through the control means inforward position, and preset means to (close the reverse dynamic brakecircuit branch and open the forward dynamic braking circuit branch whenthe forward motor circuit is energized, means to close the forwarddynamic brake circuit branch and open the reverse dynamic brake circuitbranch when the reverse motor circuit is closed, whereby "the means toprevent closure of the motor circuits is effective when the controlmeans is displaced during operation of the motor in one direction, to aposition 'to produce operation of the motor in the other direction, but'is ineffective to prevent reenergization "of a motor circuit to operatethe motor in its initial direction, said preset means including relaymechanism having a coil in each motor circuit and switch means in eachdynamic brake circuit branch, the forward relay coil when energized,closing the switch means in the reverse dynamic brake branch, and viceversa, and holding 'means to maintain each relay switch closed, once itscoil is energized, until the other coil is energized. V

5. In a control for "a reversible electric motor, control means operableto forward, reverse, and neutral positions, a forward motor energizingcircuit operated by operation of the control means to forward position,a reverse motor one-- gizing circuit operated by operation of thecontrol means to reverse positiomtthe control means being adapted toopen said circuits when it is in neutral position; ,a dynamic brakingcircuit including means to prevent closure of the forward or reverse:motor circuits when the motor is operating as a generator, said dynamicbrake circuit including two branches comprising a reverse branch adaptedto be established through the control means in reverse position and aforward branch adapted to be established through the control means inforward position, and me set means to close the reverse dynamic brakecircuit branch and open the forward dynamic braking circuit branch whenthe forward motor circuit is energized, means to close the forwarddynamic brake circuit branch and open the reverse dynamic brake circuitbranch when the reverse motor :c'ircuit is closed, whereby the means toprevent closure of the -motor circuits is effective when the controlmeans is displaced during operation or the motor in one direction toposition to produce operation of the motor in the other direction, butis ineffective to prevent reenergization of a motor circuit to operatethe motor in its initial direction, said preset means including relaymechanism having a coil in each motor circuit and switch means in eachdynamic brake circuit branch, the forward relay coil when energized,closing the switch means in the TEE verse dynamic bra ke branch, andvice versayand holding means to maintain each relay switch closed, onceits coil is energized, until the other coil is energized, said holdingmeans comprising a permanent magnet associated with each coil.

6. In a control for a reversible electric motor, control means operableto forward, reverse, and neutral positions, a forward motor energizingcircuit operated by operation of the control means to forward position,a reverse motor energizing circuit operated by operation of the controlmeans to reverse position, the control means being adapted to open saidcircuits when it is in neutral position; a dynamic braking circuitincluding means to prevent closure of the forward or reverse motorcircuits when the motor is operating as a generator, said dynamic brakecircuit including two branches comprising a reverse branch adapted to beestablished through the control means in reverse position and a forwardbranch adapted to be established through the control means in forwardposition, and preset means to close the reverse dynamic brake circuitbranch and open the forward dynamic braking circuit branch when theforward motor circuit is energized, means to close the forward dynamicbrake circuit branch and open the reverse dynamic brake circuit branchwhen the reverse motor circuit is closed, whereby the means to preventclosure of the motor circuits is efiective when the control means isdisplaced during operation of the motor in one direction to a positionto produce operation of the motor in the other direction, but isineiiectivc to prevent reenergization of a motor circuit to operate themotor in its initial direction, said control means being operable to aplurality of forward speed positions, and there being a plurality offorward speed circuits corresponding to said positions, and means toprevent energization of the motor for a higher speed operation when thecontrol means is placed in a higher speed position and the blockingmeans is effective, even after the blocking means is released by decayof dynamic brakmg.

7. In a control for a reversible electric motor; a forward and a reversesolenoid switch for controlling the direction of the motor, each havinga coil, and each having a holding switch energized upon energization ofits coil; a displaceable member operable from neutral oppositely to aplurality of forward and reverse positions, a plurality of speedswitches open when the member is in neutral position but successivelyclosed by the member in accordance with its displacement from neutral, apair of forward directional switches and a pair of reverse directionalswitches, all being open when the displaceable member is in neutralposition and each pair being closed by movement of the displaceablemember from neutral toward, but prior to, speed positions thereof in itsrespective directions, a memory relay comprising a pair of coils andswitch means, the switch means being operated to close one set ofcontacts and open the other upon predetermined energization of each ofits coils, and having means to retain the switch means in each suchposition until predetermined energization of the other coil; a blockingrelay including main coil means and blocking coil means, and a switchclosing a main set of contacts when the main coil is energized, closinga blocking set of contacts when the main coil is released, and theblocking coil being adapted to prevent closure of the main contacts bythe main coil when the blocking coil is energized by predeterminedcurrent; a circuit to energize the main blocking relay coil including afirst speed switch operated by movement of the displaceable member to afirst speed position; an energizing circuit for one of the solenoidswitch coils including a second speed switch operated by thedisplaceable member in first speed position, the main blocking relaycontact set, and one of the directional switches corresponding to thedirection of movement of the displaceable member; a holding circuitbranch for the aforesaid solenoid coil including the first speed switch,the holding switch of the solenoid, and the directional switch; acircuit energized by voltage drop in the motor circuit, including theother of the pair of directional switches, and one of the memory relaycoils to energize said latter coil and close its switch means; aplurality of different speed circuits operated by movement of thedisplaceable member beyond its first speed position, and such movementof the member being adapted to open the second-named speed switch; adynamic braking circuit from the motor operable by movement of thedisplaceable member from an operating speed position in one direction toa speed position in the opposite direction, including the seconddirectional switch in such opposite direction, the memory relay switchclosed as aforesaid, the blocking relay released contacts, and theblocking coil, said dynamic braking circuit energizing the blocking coilto prevent closure of the main blocking relay contacts so long as themotor generates a predetermined current and the dynamic braking circuitis closed as aforesaid.

8. In a control for a reversible electric motor; a forward and a reversesolenoid switch for controlling the direction of the motor, each havinga coil, and each having a holding switch energized upon energization ofits coil; a displaceable member operable from neutral oppositely to aplurality of forward and reverse positions, a plurality of speedswitches open when the member is in neutral position but successivelyclosed by the member in accordance with its displacement from neutral, apair of forward directional switches and a pair of reverse directionalswitches, all being open when the displaceable member is in neutralposition and each pair being closed by movement of the displaceablemember from neutral toward, but prior to, speed positions thereof in itsrespective directions; a memory relay comprising a pair of coils andswitch means, the switch means being operated to close one set ofcontacts and open the other upon predetermined energization of each ofits coils, and having means to retain the switch means in each suchposition until predetermined energization of the other coil; a blockingrelay including main coil and blocking coil means, and a switch closinga main set of contacts when the main coil is energized, closing ablocking set of contacts when the main coil is released, and theblocking coil being adapted to prevent closure of the main contacts bythe main coil when the blocking coil is energized by predeterminedcurrent; a circuit to energize the main blocking relay coil including afirst speed switch operated by movement of the displaceable member to afirst speed position; an energizing circuit for one of the solenoidswitch coils including a second speed switch operated by thedisplaceable member in first speed posi tion, the main blocking relaycontact set, and one oi the directional switches corresponding to thedirection or movement of the displaceable,

member; a holding circuit branch for the aforesaid solenoid coilincluding the first speed switch, the holding switch of the solenoid,and the directional switch; a circuit energized by voltage drop in themotor circuit, including the other of the pair of directional switches,and one of the memory relay coils to energize said latter coil and closeits switch means; a plurality of different speed circuits operated bymovement of the displaceable member beyond its first speed position, andsuch movement of the member being adapted to open the second-named speedswitch; a dynamic braking circuit from the motor operable by movement ofthe displaceable member from an operating speed position in onedirection to a speed position in the opposite direction, including thesecond directional switch in such opposite direction, the memory relayswitch closed as aforesaid, the blocking relay released contacts, andthe blocking coil, said dynamic braking circuit energizing the blockingcoil to prevent closure of the main blocking relay contacts so long asthe motor generates a predetermined current and the dynamic brakingcircuit is closed as aforesaid, and an additional dynamic brakingcircuit including one memory relay coil, the opposite memory relayswitch, the release contacts of the blocking relay, and the blockingrelay coil; said memory relay coils having sufficient impedance toprevent enough current from flowing through the blocking coil to enableit to block action of its main coil.

9. In a control mechanism for a reversible electric motor, control meansmovable to forward, neutral, and reverse positions, a forward and areverse circuit branch adapted to be selectively closed by said controlmeans for establishing forward and reverse motions of the motor andadapted to be opened when the control means is moved to neutral; adynamic braking circuit branch for the motor wherein the motor isadapted to operate as a generator, switch means operable to close thedynamic braking circuit branch upon movement of the control means toneutral, and additional means including a blocking coil and a relayswitch, the switch being biased upon energization of the coil toward aposition to maintain the reverse circuit branch open; and circuit branchmeans operable upon movement of the control means to reverse positionduring operation of the motor as a generator to energize the coil by thepotential so generated by the motor to prevent closure of the reversecircuit.

7 10. The combination of claim 9, wherein the first mentioned dynamicbraking circuit branch also includes the coil of the additional means,but comprises a high resistance circuit branch delimiting energizationof the coil sufficiently to hold its switch; and the second mentionedcircuit branch means comprises a low resistance branch connected toshunt said high resistance of the first branch to enable the coil to beenergized sufliciently to hold its switch to maintain the reversecircuit deenergized.

11. The combination or claim 9, wherein the relay switch of theadditional means is in the forward and the reverse circuit branches andhas a main coil energizable by operation of the control means forclosing it in the said circuit branches, and wherein the dynamic brakeswitch means is operatively connected with the switch of the additionalmeans so that (1) the main relay coil acts to close the relay witch ofthe additional means and to open the dynamic brake switch means, and (2)the relay coil of the additional means acts to hold the relay switch ofthe addi tional means open and to close the dynamic brake switch means.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,245,194 Crabbe Nov. 6, 1917 1,328,501 Eaton Jan. 20, 19202,465,332 Witte Mar. 22, 1949

